What's a good 3-day itinerary for Nanjing?

Three geographic zones, one per day. Nanjing sits on a north-south axis that makes daily clustering natural. Day 1 stays east of Zhongshan Lu. Start at the Presidential Palace by 8:30 AM, before the tour groups flood the Republic-era halls around 10. The 1912 District sits two blocks south, with a half-dozen cafe terraces for a mid-morning stop under the plane trees. Walk 15 minutes east to Nanjing Museum, founded in 1950, and give it two hours minimum. The Republic of China History gallery on the second floor is the strongest wing. Lunch at Nanjing Da Pai Dang near Hunan Lu, a 10-minute taxi ride north. Order the yanshuiya (salted duck, roughly 48 CNY) and the duck-blood vermicelli soup (ya xue fen si tang, about 22 CNY). The duck skin should feel slippery-cool, faintly briny. If it's warm and greasy, send it back. Afternoon at Xuanwu Lake park, free entry, where the breeze off the water cuts the humidity. The Ming city wall runs along the south shore. Budget about 8 km of walking for Day 1.

Day 2 belongs to Purple Mountain, called Zijin Shan locally. Take Metro Line 2 to Xiamafang station, then the scenic area shuttle to the entrance. Arrive at Sun Yat-sen Mausoleum by 8 AM. The 392 stone steps are the real workout, steep enough that your calves will remind you at dinner. Free entry, but you need to reserve a timed ticket on the Zhongshan Scenic Area WeChat mini-program at least a day ahead. By 10 AM, walk south through the forested path, about 2.5 km, to Ming Xiaoling, the mausoleum of the Hongwu Emperor. The Sacred Way lined with stone elephants and camels is the best stretch. Expect damp pine air and cicadas if you visit between May and October. Budget 30 CNY for Ming Xiaoling entry. Lunch at a canteen near the Botanical Garden east of the tombs, where noodles run 15-25 CNY. By 3 PM you'll be tired. Shuttle and Metro back to Xinjiekou for a rest. About 12 km on Day 2, most of it uphill-downhill.

Day 3 moves southwest. Start at the Memorial Hall of the Victims in Nanjing Massacre by Japanese Invaders, opened in 1985, free entry, closed Mondays. Arrive at 8:30 AM. Give it 90 minutes minimum. The hall is cold inside, literally, kept at low temperature by design. It is heavy. You will not want lunch right afterward. Walk 20 minutes east to Mochou Lake Park for a quiet reset. By noon, take Metro Line 1 south to Sanshan Jie station and walk to the Confucius Temple district along the Qinhuai River. The area is touristy, yes, but the tangbao at Qifang Ge on Gongyuan Jie are worth the crowd. About 8 CNY for four. Bite a small hole, sip the broth first, then dip in Zhenjiang vinegar. The afternoon is for Zhonghua Gate, the largest surviving Ming-era city gate in China, about 30 CNY entry. Climb for the view south over the old neighborhoods. Dinner along the river, where the lionhead meatball (shizi tou) comes in clay pots, 38-48 CNY. Day 3 covers about 10 km.

A few practical notes. Nanjing's Metro runs from roughly 6 AM to 11 PM, with single rides costing 2-7 CNY depending on distance. The Alipay Tour Pass works at turnstiles and most restaurants, so set it up before you arrive. Late September temperatures sit around 22°C with high humidity, and drizzle shows up without warning. Pack a light rain shell. English signage exists at major sites but disappears at local restaurants. Download Pleco or a translation app before you land. Solo-traveler safety sits at 6.8 out of 10 (see the TTDI Solo-Safety Index), reflecting low street crime but accounting for the language barrier outside tourist zones. Taxis are metered and reliable, with a cross-town ride rarely topping 30 CNY, about 4.50 USD at current rates.